Nanomagnetically modified sulfuric acid (γ-Fe2O3@SiO2-OSO3H): an efficient, fast, and reusable green catalyst for the Ugi-like Groebke-Blackburn-Bienaymé three-component reaction under solvent-free conditions

Superparamagnetic nanoparticles of modified sulfuric acid (γ-Fe2O3@SiO2-OSO3H) represent a straightforward and green catalyst for the rapid synthesis of aminoimidazopyridine skeletons via the Ugi-like Groebke-Blackburn-Bienaymé three-component reaction. The γ-Fe2O3@SiO2-OSO3H catalyst could be recovered and reused in five reaction cycles, giving a total TON = 453. The products were prepared under solvent-free conditions without any additives.